To supply an automobile with power once the engine is running, an automobile includes a generator. A typical generator contains a moving rotor and a stationary stator. A voltage regulator circuit supplies current to the moving rotor to generate a magnetic field in the rotor. The magnetic field from the moving rotor induces a voltage in the stator as the rotating rotor moves past the stationary stator. Typically a regulator regulates the voltage by controlling current to the rotor, thus regulating the voltage induced in the stator to produce a constant voltage for the electrical load.
Generators for automobiles typically generate a voltage of 14 volts after rectification. With electrical loads for automobiles increasing, the automobile industry is considering higher voltages, such as 42 volts.